Tissue treatment by normothermic heating

ABSTRACT

An apparatus for treating tissue in a tissue treatment area includes a heater that does not contact the tissue. The apparatus may be attached to the skin of a person to form a treatment volume about the tissue to be treated. The heater, supported at the layer, is held near the tissue to be treated, out of contact with the tissue. The apparatus includes a controller to cause the heater to raise the temperature of tissue in the tissue treatment area to a temperature in a range from a pretreatment temperature to 38° C. The controller may include means that cause the heater to operate over a therapeutic sequence, that cycle the heater on and off, that provide selectable average temperature values, that cause the heater to operate over an average temperature range, that cause the heater to operate at an average temperature over a therapy cycle, or that cause the heater to operate at an average temperature over a therapeutic sequence.

CROSS REFERENCES TO RELATED CO-PENDING APPLICATIONS

This application is a continuation application of U.S. patentapplication Ser. No. 09/778,590, filed on Feb. 7, 2001, now U.S. Pat.No. 6,423,018 which is a continuation of U.S. patent application Ser.No. 09/491,722, filed Jan. 27, 2000, now U.S. Pat. No. 6,213,966, whichis a continuation of U.S. patent application Ser. No. 09/271,822, filedMar. 18, 1999, now U.S. Pat. No. 6,113,561, which is a continuation ofU.S. patent application Ser. No. 08/786,713, filed Jan. 21, 1997, nowU.S. Pat. No. 5,964,723, which is a continuation-in-part U.S. patentapplication Ser. No. 08/356,325, filed Feb. 21, 1995, now abandoned,which is a 35 U.S.C. 371 priority application of PCT InternationalApplication Serial No. PCT/US93/05876, filed Jun. 18, 1993, which is acontinuation-in-part of, and claims priority from, U.S. Pat. applicationSer. No. 07/900,656, filed Jun. 19, 1992, now abandoned.

This application is related to the following co-pending U.S. patentapplications:

-   -   Ser. No. 09/748,418, filed Dec. 26, 2000;    -   Ser. No. 09/772,025, filed Jan. 29, 2001;    -   Ser. No. 09/771,725, filed Jan. 29, 2001;    -   Ser. No. 09/771,792, filed Jan. 29, 2001; and    -   Ser. No. 09/609,346, filed Jul. 5, 2000.

FIELD OF THE INVENTION

This invention relates to a wound covering for wound treatment and, inparticular, wound covers having a substantial portion of the wound coverin non-contact with the wound and capable of delivering heat to thewound. The wound covering preferably controls the temperature, humidityand other aspects of the environment at the wound site.

BACKGROUND OF THE INVENTION

Wounds in general, as used in this context, are breaks in the integrityof the skin of a patient. Wounds may occur by several differentmechanisms. One such mechanism is through mechanical traumatic meanssuch as cuts, tears, and abrasions. There are many instruments ofcausality for mechanical wounds, including a kitchen bread knife, brokenglass, gravel on the street, or a surgeon's scalpel. A differentmechanism cause for mechanical wounds is the variable combination ofheat and pressure, when the heat alone is insufficient to cause anoutright burn. Such wounds that result are collectively referred to aspressure sores, decubitus ulcers, or bed sores, and reflect a mechanicalinjury that is more chronic in nature.

Another type of mechanism causing a wound is vascular in origin, eitherarterial or venous. The blood flow through the affected region isaltered sufficiently to cause secondary weakening of the tissues whicheventually disrupt, forming a wound. In the case of arterial causes, theprimary difficulty is getting oxygenated blood to the affected area. Forvenous causes, the primary difficulty is fluid congestion to theaffected area which backs up, decreasing the flow of oxygenated blood.Because these wounds represent the skin manifestation of otherunderlying chronic disease processes, for example, atheroscleroticvascular disease, congestive heart failure, and diabetes, these vascularinjuries also are chronic in nature, forming wounds with ulceratedbases.

Traditional wound coverings, such as bandages, are used to mechanicallycover and assist in closing wounds. Such bandages typically cover thewound in direct contact with the wound. This may be acceptable foracute, non-infected traumatic wounds, but it must be kept in mind thatdirect bandage contact with a wound can interfere with the healingprocess. This interference is particularly prevalent for chroniculcerated wounds because of the repeated mechanical impact andinteraction of the bandage with the fragile, pressure sensitive tissueswithin the wound.

The benefits of application of heat to a wound are known, and documentedbenefits include: increased cutaneous and cutaneous blood flow,increased oxygen partial pressure at the wound site; and increasedimmune system functions, both humoral and cell mediated, includingincreased migration of white blood cells and fibroblasts to the site.

However, heat therapy for the treatment of wounds, either infected orclean, has been difficult to achieve in practice. For instance, heatinglamps have been used, but these resulted in drying of wounds, and insome cases, even burning tissue from the high heat. Due to these andother difficulties, and since most acute wounds usually heal over time,physicians no longer consider the application of heat to the wound aspart of the treatment process. The thinking among medical personnel isthat any interference in a natural process should be minimized until itis probable that the natural process is going to fail. Additionally, theavailability of antibiotics for use in association with infected woundshas taken precedence over other therapies for the treatment of chronicwounds and topical infections.

In French patent number 1,527,887 issued Apr. 29, 1968 to Veilhan thereis disclosed a covering with a rigid oval dome, its edge restingdirectly on the patient's skin. One aspect of the Veilhan woundprotector is a single oval heating element resting on the outer surfaceof the rigid dome, positioned at the periphery of the rigid dome.Veilhan does not discuss the heating aspect other than to state that itis a component.

The benefits of controlling other environmental parameters around thewound site are not as well known. Controlling the humidity at the woundsite and the benefits of isolating the wound have not been extensivelystudied and documented.

While the benefit of applying heat to wounds is generally known, themanner of how that heat should be used or applied is not knownHistorically, heat was applied at higher temperatures with the goal ofmaking the wound hyperthermic. These higher temperatures often resultedin increasing tissue damage rather than their intended purpose of woundtherapy and healing. There is a need for appropriate wound caremanagement incorporating a heating regimen that is conducive to woundhealing, yet safe and cost effective.

SUMMARY OF THE INVENTION

The present invention disclosed herein approaches the treatment ofwounds with heat based on an understanding of physiology. The normalcore temperature of the human body, defined herein for purposes of thisdisclosure, is 37° C.±1° C. (36°-38° C.), which represents the normalrange of core temperatures for the human population. For purposes ofdiscussion and this disclosure, normal core temperature is the same asnormothermia. Depending on the environmental ambient temperature,insulative clothing and location on the body, skin temperature typicallyranges between about 32° C. and about 37° C. From a physiologic point ofview, a 32° C. skin temperature of the healthy distal leg is moderatehypothermia. The skin of the distal leg of a patient with vascularinsufficiency may be as low as 25° C. under normal conditions, which issevere hypothermia.

A fundamental physiologic premise is that all cellular physiologicfunctions, biochemical and enzymatic reactions in the human body areoptimal at normal body core temperature. The importance of this premiseis seen in how tightly core temperature is regulated. Normalthermoregulatory responses occur when the core temperature changes aslittle as ±0.1° C. However, the skin, as noted above, is usuallyhypothermic to varying degrees. For example, the skin of the torso isusually only slightly hypothermic, whereas the skin of the lower legs isalways hypothermic. Consequently, wounds and ulcers of the skin,regardless of location, are usually hypothermic. This skin hypothermiaslows cellular functions and biochemical reactions, inhibiting woundhealing.

The effects of hypothermia on healing are well known. A number ofregulatory systems within a human are affected, such as the immunesystem and coagulation, with both platelet function as well as theclotting cascade affected. Patients with hypothermic wounds experiencemore infections which are more difficult to treat, have increasedbleeding times and have been shown to require more transfusions ofblood. All of these complications increase morbidity and the cost ofpatient care and, to a lesser extent, increase the likelihood ofmortality.

One purpose of the present invention is to raise the wound tissue and/orperiwound tissue temperatures toward normothermia to promote a moreoptimal healing environment. The present invention is not a “heatingtherapy”, per se, where it is the intent of “heating therapy” to heatthe tissue above normothermia to hyperthermia levels. Rather, thepresent invention is intended to bring the wound and periwound tissuestoward normothermia without exceeding normothermia.

The medical community has not historically considered normothermicheating to be therapeutic. Many physicians feel that hypothermia isprotective and, therefore, desirable. Studies with the present inventionwould indicate that this widely held belief that hypothermia is at leastbenign or possibly beneficial is incorrect with regard to wound healing.

The present invention is a wound covering for application to a selectedtreatment area of a patient's body that includes, at least as a portionof the selected treatment area, a target tissue of a selected woundarea. The selected treatment area may also include a portion of the areaimmediately proximate to the wound area referred to as the periwoundarea. The wound covering comprises a heater suitable for providing heatto at least a portion of the selected treatment area, an attachment forattaching the heater in a non-contact position proximate the selectedtreatment area, a heater controller, connected to the heater andincluding a power source for the heater, for controlling the heater, andan input control to the heater controller providing guidance to theheater controller so as to heat the wound and/or periwound tissue to atemperature in a range from a pretreatment temperature to about 38° C.Pretreatment temperature is that temperature the wound tissue is at whentherapy begins and is usually somewhat above ambient temperature andalso is variably dependent on where the wound is located on a patient'sbody skin surface. The ambient temperature is that temperature of theenvironment immediately around the selected treatment area not a part ofthe patient's body, i.e., the bed, the air in the room, the patient'sclothing.

The heater is selectable from among several types of heat sources suchas warmed gases directed over the selected treatment area and electricalheater arrays placed proximate the selected treatment area. Electricalheater arrays are adaptable for construction into a layer of variableproportion and geometry or as a point source. The present inventionanticipates the ability to provide several different sizes and geometricconfigurations for the heater. The present invention is flexible inbeing able to provide uniform heating over the entire selected treatmentarea or provide a non-uniform heating distribution over selectedportions of the selected treatment area. Alternate heat sourceembodiments could include warm water pads, exothermic chemical heatingpads, phase-change salt pads, or other heat source materials.

The present invention anticipates that the controller is able to controlboth the temperature and the duration of the application of heat. Thiscontrol may extend from manual to fully automatic. Manual controlanticipates the controller maintaining the heater temperature at anoperator-selected temperature for as long as the operator leaves theheater on. More automatic modes provide the operator an ability to enterduty cycles, to set opt t as well as to define therapy cycles andtherapeutic sequences. As used herein, a duty cycle is a single on cyclewhen heating of the heater is occurring, measured from the beginning ofthe on cycle to the end of that on cycle. A heater cycle is a singlecomplete on/off cycle measured from the beginning of a duty cycle to thebeginning of the next duty cycle. Consequently, a duty cycle may also berepresented in a percentage of, or as a ratio of the time on over thetime off. A plurality of heater cycles are used to maintain heatertemperature around a selectable temperature set point during a therapycycle which is defined as an “on” period, composed of a plurality ofheater cycles, and an “off” period equivalent to remaining off for anextended period of time. A therapeutic sequence, as used herein, is alonger period of time usually involving a plurality of therapy cyclesspread out over an extended period of time, the most obvious being a dayin length. The present invention anticipates the use of any period oftime as a therapeutic sequence and involving one, or more than onetherapy cycles.

The present invention also anticipates programmability for a number ofmodalities including peak heater temperature for a duty cycle and/ortherapy cycle, average heater temperature for a duty cycle and/ortherapy cycle, minimum heater temperature for a heater cycle and/ortherapy cycle, ratio of duty cycle, length of therapy cycle, number ofduty cycles within a therapy cycle, and number of therapy cycles in atherapeutic sequence. Different duty cycles within a therapy cycle maybe programmed to have different peak heater temperatures and/or heatercycles may have average heater temperatures over that therapy cycle.Different therapy cycles within a therapeutic sequence may be programmedto have different peak heater temperatures and/or average heatertemperature over each therapy cycle. The wound covering control isoperator-programmable or may have preprogrammed duty cycles, therapycycles, and therapeutic sequences selectable by the operator.

The input control may take several forms. One form of input control is atemperature feedback from a temperature sensor placed proximate theselected area of treatment to monitor the target tissue temperatureresponse. The sensor provides to the input control, a sequence oftemperature values for the target tissue of the selected treatment areaProgrammability may provide for variable heater output dependent on theactual target tissue temperature as well as the rate of target tissuetemperature change within the selected treatment area

Another form of input control is for the controller of the presentinvention to follow a temperature treatment paradigm programmable withinthe controller which is based on one or more parameters derivedempirically, such as: the thermodynamic characteristic of tissue, theheat conduction rate of tissue types, the wound location, the woundtype, the wound stage, the wound blood flow, the tissue surface areainvolved in the selected treatment area, the tissue volume involved inthe selected treatment area, the heater geometry, the heater output, theheater surface area, and the ambient temperature. This paradigmprogramming provides an operator the ability, when selecting a treatmentmode or method, to take into account all of these parameters. Moreimportantly, the operator is able to tailor a treatment mode based onthe type of wound to be treated. For example, wound types, such aswounds secondary to arterial insufficiency versus those secondary tovenous insufficiency, or the location of the tissue on the body, forexample, the leg versus the sacrum or abdomen, are sufficientlydifferent so as to necessitate different heater treatment methods thattake into account the myriad number of differences between wound types.One or more parameters are inputted to the controller to provide asequence of target tissue temperatures over time to the heatercontroller based on the parameters used.

A preferred form of the wound covering includes an attachment as aperipheral sealing ring which, in use, completely surrounds the area ofthe wound and periwound, i.e., the selected treatment area. The uppersurface of the peripheral sealing ring is spanned by a continuous layerwhich is preferably transparent and substantially impermeable, althoughthe present invention also anticipates the use of a gas permeable layersuitable for some applications. Once in position, the sealing ring andthe layer define a wound treatment volume which surrounds the wound.Additionally, the layer spanning the peripheral sealing ring may besealed about the periphery of the sealing ring and act as a barrierlayer over the wound treatment volume. Optionally, the heater may beincorporated into the barrier layer or the barrier layer may beincorporated into the heater. An adhesive and a suitable release lineris applied to the lower surface of the peripheral sealing ring tofacilitate the application of the wound covering to the patient's skin.

The barrier layer may include a pocket adapted to receive an activeheater. An alternate form of the invention provides for the transport ofheated air from a remote heat source to the wound treatment volume. Inthe active heater embodiments a thermostat and/or a pressure-activatedswitch may be used to control the heating effects of the heater.Passively heated embodiments are contemplated as well. These passiveversions of the device include the use of thermally insulating coveringswhich retain body heat within the treatment volume. These reflectors orinsulators may be placed in a pocket formed in the barrier layer. Eachof these heated embodiments promote wound healing by maintaining thewound site at a generally elevated, but controlled, temperature.

In general, the peripheral sealing ring is made from an absorbentmaterial which may act as a reservoir to retain and/or dispense moistureinto the treatment volume increasing the humidity at the wound site. Thereservoir may also contain and deliver medicaments and the like topromote healing.

The present invention is designed to directly elevate the temperature ofthe hypothermic skin and subcutaneous tissue of the selected wound areato a temperate which is close to or at normothermia. The purpose of thisdevice is to create within the wound and periwound tissues of theselected treatment area a more normal physiologic condition,specifically a more normothermic condition, which is conducive to betterwound healing. The present invention anticipates the use of an activeheater that creates a heat gradient from heater to wound and periwoundtissues. The usual temperature gradient for tissues goes from about 37°C. deep in the body core down to about 32° C. at the skin surface of theleg. The heater of the present invention operates in an output rangesuitable to rake the temperature of the selected treatment tissue fromits pretreatment temperature to not more than 38° C.

In contrast, typical local heating therapy (e.g. hot water bottles, hotwater pads, chemical warmers, infrared lamps) deliver temperaturesgreater than 46° C. to the skin. The goal of traditional heating therapyis to heat the tissue above normal, to hyperthermic temperatures.

The present invention differs from infrared lamps in two ways. First,the present invention includes a dome over the wound that is relativelyimpermeable to water vapor transmission. After application of thebandage, moisture from the intact skin or wound evaporates, and airwithin the dome quickly reaches 100% relative humidity. The interior ofthe present invention is now warm and humid. For example, a 2.5 squareinch bandage at 28° C. requires only 0.0014 g of water to reachsaturation. When the air is thus saturated, no further evaporation canoccur and, therefore, no dying of the wound can occur. This equilibriumwill be maintained as long as the bandage is attached to the patient.

When heat is provided by the preferred embodiment of the presentinvention, the absolute amount of water needed to reach 100% relativehumidity is slightly increased since warm air has a greater capacity forholding moisture. However, the air within the dome of the bandage stillreaches water vapor saturation very quickly, and no further evaporationoccurs. For example, a 2.5 square inch bandage of the present inventionat 38° C. requires only 0.0024 g of water to reach saturation. Excessmoisture is absorbed by the foam ring, but still is retained within thebandage. The enclosed dome design maintains 100% humidity over the woundwhich also prevents evaporation due to the heat. As long as the humidityis retained within the bandage, heating therapy could theoretically becontinued indefinitely without causing the wound to dry. In contrast,when using infrared lamps, the wounds are open and exposed to theenvironment. The result is excessive drying of the wound, increasingtissue damage.

Secondly, the present invention operates at low temperatures, from aboveambient to about 38° C. This causes only minimal heating of the skin. Incontrast, infrared lamps operate at temperatures in excess of 200° C.These lamps heat the wound to hyperthermic temperatures which can causethermal damage to the tissue of the wound.

At the low (normothermic) operating temperatures of the presentinvention, the heat transfer to the skin is minimal. The low wattageheater, the inefficiencies of the heat transfer into the tissue, thethermal mass of the tissue and the blood flow (even if markedlyreduced), all prevent the wound temperature from reaching the heatertemperature. Hypothermic wound tissue is warmed as a result of“migration” of the body's core temperature zone toward the local woundarea.

The following data document the tissue temperatures resulting from a 38°C. heater of the present invention on:

Average Maximum Normally perfused human skin 36° C. 36° C.Arterial/diabetic foot ulcers 32° C. 35° C. Venous/arterial leg/footulcers 33° C. 35° C. Non-perfused human model 35° C. 35° C.

When warmed with a 38° C. heater, wounds on poorly perfused legs reachstable average temperatures of 32-33° C. In contrast, normally perfusedskin reaches 36° C. It is important to note that these data arecontradictory to the assumption that poorly perfused tissue would reacha higher temperature than normally perfused tissue. This resultsubstantiates the physiologic finding that the “migration” of the coretemperature zone toward the local wound zone, decreasing the gradientdifference between the core and surface temperature, is the cause forthe observed increased wound temperatures. Core temperature regulationis heavily dependent on perfusion, and migration of the core temperaturezone is also heavily dependent on perfusion. At no point in time did thepoorly perfused tissue reach normothermia. Consequently, poorly perfusedlegs are much colder than normally perfused legs, and, thus, poorlyperfused legs constitute a substantially deeper heat-sink.

A wound-healing pilot study is under way, studying patients with chronicarterial and/or venous ulcers of the lower leg. These patients havesuffered from these ulcers for many months and, in some cases, evenyears, despite aggressive medical and surgical therapy. Of 29 patientsenrolled, 24 have completed the study protocol or are still beingtreated. Of these 24 patients, 29% are completely healed, and 38% show asignificant reduction of the wound size within 2-5 weeks of receivingtherapy with the present invention.

A known consequence of restoring normothermia to tissues is to inducesome degree of vasodilatation which increases local blood flow.Preliminary data collected during trials of the present invention,studying the effects of the present invention on normal subjects and onwound healing has borne this out. An added effect has been to increasethe partial pressure of oxygen in the subcutaneous tissues (P_(sq)O₂),which is an indirect indicator of the status of the tissue. The higherthe P_(sq)O₂, the greater the likelihood the tissue will benefit andimprove the healing process. The results of some of these studies arepresented in Tables 1-4.

In conducting the studies presented in Tables 1-4, a wound coveringaccording to the present invention is placed over the skin. Thetemperature of the subcutaneous tissue is then measured over time. From−60 minutes to the 0 minute mark, the heater is off in order to obtain abaseline temperature. At the 0 minute mark the heater is activated andits temperature kept constant over the next 120 minutes when it isturned off. Temperature measurements were taken during this 120 minuteperiod and for an additional 180 minutes after turning the heater off.As shown in Table 1, with activation of the heater to 38° C., thesubcutaneous tissue temperature rapidly rose from about 34.3° C. toabout 36° C. over the first 30 minutes. The temperature of thesubcutaneous tissue continued to slowly raise over the next 90 minutesto a temperature of about 36.7° C. After turning the heater off, thetemperature of the subcutaneous tissue fell to about 35.9° C. and heldthis temperature fairly uniformly for at least the next 120 minutes.

Table 2 presents the skin temperature data collected from within thewound cover of the present invention for the same periods as those inTable 1. The general curve shape is similar to the subcutaneous tissuetemperature curve. The baseline temperature at the 0 minute mark wasabout 33.5° C. After turning the heater on to 38° C., the skintemperature rose rapidly to about 35.8° C. in the first 30 minutes, thenslowly rose to about 36.2° C. by the end of the 120 minute heatingperiod. After turning the heater off, the skin temperature fell to about35° C. and held there for at least the next two hours.

Table3 represents laser Doppler data collected from the tissue duringthe experiments and correlates to blood flow through the local areabeing treated with heat The baseline flow is approximately 80 ml/100g/min and rises to about 200 ml/100 g/min at its peak, half way throughthe heating period. The flow “normalizes” back to baseline during thelast half of the heating period and remains at about baseline for theremainder of the measuring period.

The change in P_(sq)O₂ is followed in Table 4. The baseline P_(sq)O₂ isabout 75 when heating begins and rises steadily to about 130 by the endof the heating period. The P_(sq)O₂ remains at this level for theremainder of the measuring period despite the lack of heating for thelast 180 minutes. The added benefit of increased P_(sq)O₂ by heatingcontinues well into the period of time after active heating has ceased.Wounds will continue to benefit from the effects of heating forsubstantial periods of time after the heating is turned off. Theconsequences of this study with the present invention is that theheating need not be constant, but deliverable over a heater therapycycle or cycles that may or may not be part of a larger therapeuticsequence.

Similar trials were conducted using a heater temperature of 46° C. Thisdata is presented in tables 5-8. Only slight additional benefits werefound in any of the four measured parameters when studied at this highertemperature. The benefits imparted by active heating according to thepresent invention seem to peak at about 46° C. In many instances, 43° C.appears to be the optimal temperature for maximal efficiency in terms ofleast energy required for the greatest therapeutic gain.

Our initial human clinical data shows that the beneficial effects ofheating on blood flow and P_(sq) 0 ₂ last at least one hour longer thanthe actual duration of heat application. Further, we have noted thatcycled heating seems to be more effective for wound healing thancontinuous heating. Therefore, the data recommends cycling the heater ina therapy cycle (e.g. 1 hour “on” and 1 hour “off”) for a total heatingtime of 2-8 hours per day as a therapeutic sequence.

None of the 29 patients with compromised circulation treated to datehave shown any indication of skin damage due to 38° C. heat.Furthermore, none of these wounds have exceeded 35° C. tissuetemperature, with an average wound temperature of 32-33° C. The presentinvention raises the wound temperature toward normothermia, but even ona poorly perfused leg, the tissue does not reach normothermia.

Accordingly, the invention concerns an apparatus for heating tissue in atissue treatment area from a level that does not contact the tissue.This apparatus has a layer out of contact with the tissue at which aheater is located. The apparatus may be attached to the skin of a personto form a treatment volume about the tissue. The heater, supported atthe layer, is held near the tissue to be treated, out of contact withthe tissue for raising the temperature of the tissue in the tissuetreatment area. The apparatus includes a controller to cause the heaterto raise the temperature of the tissue to a temperature in a range froma pretreatment temperature to 38° C.

BRIEF DESCRIPTION OF THE DRAWINGS

Illustrative but not limiting embodiments of the invention are shown inthe attached drawings. Throughout the several figures like referencenumerals refer to identical structure throughout, in which:

FIG. 1A is an exploded view of a wound covering according to the presentinvention;

FIG. 1B illustrates an assembled view of the wound covering of FIG. 1A;

FIG. 2A is a view of an alternate wound covering;

FIG. 2B is a view of an alternate wound covering of FIG. 2A with passiveheating card inserted in the wound covering;

FIG. 3A is an exploded view of an additional alternate wound covering,

FIG. 3B is an assembled view of the wound covering of FIG. 3A;

FIG. 4 is a side elevation view of a wound covering;

FIG. 5 is an enlarged top plan view of a wound covering,

FIG. 6 is an enlarged sectional view taken along line 6—6 of FIG. 5;

FIG. 7 is a bottom view of the wound covering of FIG. 4;

FIG. 8A is an exploded view of an alternate wound covering.

FIG. 8B is an assembly view showing the air flow through the woundcovering;

FIG. 9A is a perspective view of an alternate wound covering,

FIG. 9B is a side view of the wound covering of FIG. 9A;

FIG. 10 is a perspective view of an alternate wound covering;

FIG. 11A is a perspective view of an alternate wound covering,

FIG. 11B is a side elevational view of the wound covering of FIG. 11A;

FIG. 11C is a view of the wound covering of FIG. 11A;

FIG. 12 is a perspective view of an alternate connector apparatus forthe wound covering;

FIG. 13A is an alternate connector arrangement for the wound covering;

FIG. 13B is a side sectional view of the wound covering of FIG. 13A;

FIG. 14 is a view of a rigid connector for engagement with a woundcovering;

FIG. 15 is an alternate fluid inlet line for the wound covering;

FIG. 16A is a view of a two ply barrier layer wound covering,

FIG. 16B is a side elevational view of the wound covering of FIG. 16A;

FIG. 17 is an alternate wound covering;

FIG. 18A is an alternate wound covering;

FIG. 18B is a side sectional view of the wound covering of FIG. 18A;

FIG. 19 is a side elevational view of an alternate wound covering

FIG. 20 is a schematic diagram of an embodiment of the presentinvention; and

FIG. 21A is a schematic representation of an alternate embodiment of theheater array distribution shown in FIG. 20;

FIG. 21B is a schematic representation of an alternate embodiment of theheater array distribution shown in FIGS. 20 and 21A;

FIG. 21C is a schematic representation of an alternate embodiment of theheater array distribution shown in FIGS. 20, 21A, and 21B;

FIG. 21D is a schematic representation of an alternate embodiment of theheater array distribution shown in FIGS. 20, 21A, 21B, and 21C;

FIG. 22 is a graphical representative sample of an operational schemefor an embodiment of the present invention, such as the embodiment shownin FIG. 20;

FIG. 23 is a graphical representative sample of an additionaloperational scheme for an embodiment of the present invention, such asthe embodiment shown in FIG. 20 using the scheme depicted in FIG. 22;and

FIG. 24 is a graphical representative sample of another additionaloperational scheme for an embodiment of the present invention, such asthe embodiment shown in FIG. 20 using the schemes depicted in FIGS. 22and 23.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to a non-contact wound covering forcontrolling the local environment at a wound site on a patient. A woundsite includes those portions of the patient's skin obviously definableas the wound area and the immediately adjacent periwound area as theselected treatment area of the wound site. The wound covering protectsthe wound from contamination by materials from the outside environmentand also prevents the wound site from shedding contaminants into thelocal environment of the patient, i.e. the hospital room. The treatmentvolume formed proximate the wound site can be controlled to create anoptimal healing environment. The word “wound” as used herein refersgenerically to surgical incisions, ulcers, or other lesions or breaks inthe skin.

First, a substantially vertical wall is provided to encircle theselected treatment area on the surface of the patient's skin. Thisvertical wall provides an upper surface to support a layer spanning thisstructure above the level of the wound and a lower surface suitable forattachment to the patient's skin. This structure is referred tothroughout as an attachment or a peripheral sealing ring. Together theseelements form a wound treatment volume between the layer and the surfaceof the selected treatment area. The fact that the layer does not contactthe wound itself promotes healing by minimizing mechanical stresses onthe tissues. The lower surface suitable for attaching to the skin mayinclude an adhesive and a complimentary release liner assembly tofacilitate the attachment of the wound covering to the skin of thepatient. The present invention anticipates using a heater such that thelayer may comprise the heater formed as the layer or as a layer whichincludes a heater within some portion of the layer. The layer may alsoinclude functioning as a barrier layer completely enclosing the woundtreatment volume.

In accordance with the present invention, the climate within the woundtreatment volume may be controlled. Typically the temperature, humidity,and gas composition, for example adding oxygen, nitric oxide or ozone,are controlled. Also, aerosolized medications or compounds may bereleased into this volume as well. The above list is exemplary of theclimate controls which may promote healing of the wound, and is notintended to limit the scope of the present invention. It will beunderstood by those skilled in the art that numerous other climatefactors can be controlled within the treatment volume of the presentwound covering system without departing from the scope of the invention.

FIG. 1A illustrates an exploded view of a wound covering 50. In thisembodiment, a peripheral sealing ring 52 is substantially square inoutline. Peripheral sealing ring 52 is intended to be attached touninjured skin surrounding a selected treatment area 54 using anadhesive 56. In this embodiment, a layer of adhesive hydrogel is shownas the adhesive 56. Additionally, peripheral sealing ring 52 ispreferably constructed of an open cell hydrophilic foam plastic having asealed outer surface 58 which isolates the wound from the environment.The peripheral sealing ring is fabricated from a material which mayconform to the curved surface of the patient's body. An inner surface 60of sealing ring 52 is preferably porous or absorbent so that it can forma reservoir to contain and release moisture or water vapor into the airwithin a treatment volume 62 to create a high humidity environment ifdesired. Additionally, the hydrophilic absorbent nature of peripheralsealing ring 52 absorbs fluids and blood weeping from the wound.

A layer 64 is preferably attached to an upper surface 66 of peripheralsealing ring 52 as a barrier layer to seal treatment volume 62. Layer 64is preferably constructed of a flexible synthetic polymeric film, suchas polyethylene, polyvinyl chloride, polyurethane, or polypropylene.Additionally, other polymeric films, natural and semi-synthetic, thatare suitable for use in medical applications such as cellulose andcellulose acetate, may be used. A wound tracing grid 68, alsoconstructed of a substantially clear flexible material, may optionallybe used as, or attached to, layer 64 to facilitate wound care managementso that the physician can draw an outline of the wound as an aid totracking the healing process of the wound. The wound tracing gridpreferably contains a labeling area 70 for identifying the patient, datewhen the wound was traced, and other patient medical data.

It will be understood by those skilled in the art that the volume ofperipheral sealing ring 52 will depend on the structural strength of thesupport material and the amount of fluid absorption desired.Additionally, the total area of peripheral sealing ring 52 is dependenton the size of the wound. For example, larger wounds and more flexiblecovers will require a thicker sealing ring so that the center of thecover does not touch the wound.

Upper surface 66 of peripheral sealing ring 52 is preferably sealed byextending barrier layer 64 over the entire area of upper surface 66 asshown in FIGS. 1A and 1B. Adhesive 56 for attaching peripheral sealingring 52 to uninjured skin surrounding selected treatment area 54 maytake any form, however, the preferred adhesive is preferably a two-facedhydrogel which attaches to a lower surface 72 of peripheral sealing ring52. This adhesive 56 permits the attachment of peripheral sealing ring52 to the patient's skin. Finally, peripheral sealing ring 52 may serveas a reservoir for retaining water or medicaments in treatment volume 62in order to maintain a high humidity in the air within the volume. Watermay be added to peripheral sealing ring 52 at any time during treatment.

It will be understood by those skilled in the art that peripheralsealing ring 52 can be supplied in a variety of shapes and sizes toaccommodate various wounds. The shapes may include circles, squares, orrectangles. Although it is preferred to dispense the wound covering as aunitary assembly it should be apparent that individual segments ofperipheral ring material could be assembled into any shape necessary toform a perimeter around the wound area. Likewise, barrier layer 64 andwound tracing grid 68 could be provided in large sheets which may be cutto size and then attached to the peripheral sealing ring.

FIG. 1B is an assembled view of wound covering 50 of FIG. 1A. Todispense the assembled product, a release liner 74 of FIG. 1B is appliedto adhesive 56 in FIG. 1A. Release liner 74 may span the entire lowersurface of the covering to maintain the sterility of treatment volume62. Release liner 74 preferably has a grip tab 76 to facilitate removalof release liner 74 from wound covering 50 immediately prior toapplication of wound covering 50 to the skin of a patient.

FIGS. 2A and 2B illustrate an alternate embodiment of the presentinvention as a wound covering 80 utilizing passive heating of thetreatment volume 62. Because heat is constantly being radiated from thepatient's skin surface, the insulation properties of the trapped airwithin treatment volume 62 will reduce this heat loss. By adding aninfrared reflector 82 over treatment volume 62, the infrared heat fromthe body can be reflected back to the skin for added passive heating.

An edge 84 of wound tracing grid 86 is preferably not attached to thebarrier layer to form an envelope or a pocket 94 between the woundtracing grid 86 and the barrier layer. A piece of reflective foilmaterial 88 may be inserted into pocket 94. A thin layer of insulatingmaterial 90 may be optionally attached to foil layer 88 to enhance heatretention and to provide foil layer 88 with additional resiliency. A tab92 is preferably attached to infrared reflector 82 to allow easyinsertion and removal from pocket 94 and wound covering 80.

FIGS. 3A and 3B illustrate a preferred alternate embodiment of anon-contact wound covering 108 utilizing active heating of a treatmentvolume 112. Wounds may be safely and easily heated utilizing a heaterassembly 100. Heater assembly 100 alternatively comprises apressure-sensitive switch 102,an insulating layer 104, and a foil heater106.

Pressure-sensitive switch 102 is optionally laminated to the uppersurface of heater assembly 100. The purpose of switch 102 is to shut offpower to foil heater 106 in the event that external pressure is appliedto wound covering 108 with sufficient force to cause foil heater 106 tocontact the skin or wound below. This feature prevents the possibilityof applying heat and pressure to the skin at the same time. Thecombination of heat and pressure is known to cause burns even at lowtemperatures (40° C.) because the pressure prevents blood flow in theskin making it susceptible to thermal injury. Pressure-sensitive switch102 preferably covers the entire area of heater assembly 100 so thatpressure applied anywhere to the surface of heater assembly 100 willdeactivate foil heater 106.

It will be understood by those skilled in the art that a variety ofdevices are suitable for use as pressure-sensitive switch 102. Forcesensing resistors, resembling a membrane switch, which change resistanceinversely with applied force are one such example of a pressuresensitive switch. Devices of this type offer the substantial advantageof being low cost, flexible, and durable. A variety of other forcesensing switch devices may be utilized as well.

An alternative safety feature anticipated by the present invention is amonitoring function for detecting dramatic increases in powerutilization by the heater trying to maintain an operating temperature.Under normal operation, the heater is in a non-contact positionproximate the selected treatment area and the heater will have beenprogrammed to operate at a temperature that may be either a straighttemperature value or an averaged value for either a duty cycle, therapycycle or therapeutic sequence. If physical pressure is placed on theheater and it comes into contact with the patient's body, there will bea considerable increase in the rate of heat loss from the heater becauseof the body's greater heat sink capacity. The heater controller wouldsense this drop in temperature and initially adjust either the dutycycle ratio or power output, or both, in an attempt to compensate forthe increase rate of loss. The safety aspect of this monitoring functionwould be to override this increase and turn off the device, thuspreventing heating the tissue while in direct contact with, and underpressure from, the heater.

Heater element 106 is preferably a thin film type resistance heaterwhich is commercially available. Such thin film resistance heatersutilize low voltage, minimizing the electrical risk to the patient andallowing for battery-powered mobility. Foil heater 106 is preferablysized for each wound covering 108. In actual use, foil heater 106 ispreferably provided in sheets with a pair of electrical leads 110 alongone edge. While an electrical resistance heater is the preferredembodiment of the invention, other heating devices are anticipated suchas warm water pads, exothermic chemical heating pads, and phase-changesalt pads.

Heater assembly 100 is preferably insertable into a pocket 114 formedbetween wound tracing grid 86 and the barrier layer as discussed above.Finally, a temperature monitoring device, such as a liquid crystaltemperature monitor, may be applied to an upper surface of heaterassembly 100 or within treatment volume 112 to monitor the temperaturewithin treatment volume 112.

FIGS. 4-7 illustrate an alternate embodiment of wound covering 10. Inthis embodiment, wound covering 10 includes a generally circular head,designated generally at 12, which transitions to an elongatednon-kinking, collapsible air supply or hose 14.

The apparatus, as illustrated in FIG. 4, is connected by suitable supplyline or tube 16 to a source 18 of thermally controlled air which isschematically illustrated. The term air as used herein is intended toencompass mixtures of gases of controlled composition. The apparatus isconstructed to apply a continuous stream of thermally controlled air toa wound treatment volume.

The specific form of the apparatus and details of construction can bestbe understood by reference to the various figures. The overallappearance of the wound covering is best seen in FIG. 4 and FIG. 5. Itis preferred to construct the apparatus from top and bottom sheets ofthin heat-sealable polymer film which overlay one another. A top sheetor membrane 20 overlies a bottom sheet or membrane 22 which are heatsealed together along a plurality of seal lines, including a continuousouter seam 24, which extends in a circle around head 12 and continues ina sinusoidal or convoluted fashion along and forming hose 14. An innercontinuous circular seam 26 is provided as best seen in FIGS. 6 and 7.This inner seam 26 secures the sheets together along a continuous circleto form the inner wall of a torus defining a supply volume 28.

The inner circular portion of the two sheets 20, 22 lying in the planewithin the center of the supply volume 28 forms a wall 30 separating alower wound treatment volume 32 from an upper insulation chamber 34.Wall 30 includes a plurality of apertures 36 formed by making smallcircular seals 38 and cutting and removing circular portions within thecircular seals 38. Thus, wall 30, with a plurality of apertures 36, isformed between the wound treatment volume 32 and insulation chamber 34.A plurality of apertures 40 are formed in the common circular wallsurrounding treatment volume 32 for distributing and conveying heatedair or gases from supply volume 28 into wound treatment volume 32.

The heated air flowing into treatment volume 32 bathes the wound surfaceof a patient's body 42. The air circulates throughout wound treatmentvolume 32, and then passes through apertures 36 into the upper orinsulating chamber 34, where it then passes through a filter 44 formingan outer wall of insulation chamber 34. Filter 44 filters the airleaving wound treatment volume 32, trapping contaminants shed from thewound. Filter 44 may be constructed of a filter paper bonded along itsperiphery to the outer tangential walls of head 12 forming the torus.The filter paper also provides an insulating layer which suppresses lossof heat by radiation through upper wall 30.

The lower surface of the head 12 as shown in FIGS. 6 and 7 is providedwith a peripheral sealing ring 46 made of an absorbent material such asfoam and bonded by a suitable adhesive to the walls of head 12 and skin42 of the patient around the wound. Preferably, foam or cottonperipheral sealing ring 46 is provided with a peel-off tape so that itadheres to the wall of the housing and on the other side to the skin ofthe patient. The adhesive or tape holds the apparatus in place andprevents airflow escape between the device and the skin of the patient.The absorbent material of the ring absorbs weeping blood and fluids andinsulates the skin from direct conduction of heat from head 12.

Hose 14 is designed to be non-kinking by forming it of symmetricallyconvoluted flexible material. The hose and housing are integrally formedessentially of a unitary structure, such as a thin film membrane. Hose14 is inflatable upon the application of heated air through supply line16. The indentations in hose 14 permit it to bend without kinking and,thus, differentiate from a straight tubular hose which may kink whenbent.

Since the thermal body treatment apparatus of the invention and thesupply hose section are formed from two, thin, sealed-togethermembranes, the hose, and in fact the entire apparatus, is collapsible.This prevents the possibility of applying heat and pressure to the skinas might happen if a patient rolled over on the device. Instead, theweight of the patient's body collapses the device, obstructing the flowof air, and preventing the application of heat.

The film membrane may preferably be transparent to enable viewing thewound without removal. However for cosmetic reasons the layer may beopaque. Filter paper 44 is attached across the tangential surfaces ofthe toroidal housing, thus providing a large area of filter for theescaping air. Head 12 of the apparatus may be about one foot in diameterfor most applications. However, it may be made smaller for certain otherapplications.

FIG. 8A illustrates an exploded view of an alternate embodiment of anon-contact wound covering 120 with climate control within a treatmentvolume 122 as shown in FIG. 8B. An inflatable structure 124 ispreferably attached to a fluid inlet line 126 at a fluid inlet port 129on the perimeter of inflatable structure 124. Inflatable structure 124is preferably attached to an absorbent peripheral sealing ring 128,which is in turn attached to a wound area 54 by a suitable adhesive 56.Peripheral sealing ring 128 preferably has a sealed outer surface and aporous inner surface which performs the same function as peripheralsealing ring 52 discussed above. A barrier layer 130 having an exhaustfilter 132 is attached to a top surface 134 on inflatable structure 124.

Turning now to the assembly illustrated in FIG. 8B, a gas, illustratedby direction arrows “A”, is introduced into inflatable structure 124from an external source (not shown) through inlet line 126. The gaspressurizes inflatable structure 124 in order to maintain barrier layer130 and exhaust filter 132 in an elevated position relative to woundarea 54. An inner surface 136 of inflatable structure 124 preferably hasa plurality of apertures 138 through which the fluid is introduced intowound treatment volume 122. As pressure within the treatment chamberincreases, excess pressure is relieved through exhaust filter 132. Inthis fashion, various fluids or gases can be introduced into woundtreatment volume 122.

The use of the term “fluid” in the context of this application refers toboth liquid and gaseous materials, and combinations thereof. In oneembodiment, oxygen may be introduced into treatment volume 122 throughapertures 138 of inflatable structure 124. The presence of oxygen withinwound treatment volume 122 may increase the oxygen available to thesuperficial layer of growing cells in wound area 54. Nitric oxidealternatively may be infused into treatment volume 122. Nitric oxide(NO) is a potent vasodilator which in theory may be absorbed across thewound surface and increase localized blood flow. A very smallconcentration of NO (parts per million) may provide this effect. NO mayalso be pre-absorbed into absorbent peripheral sealing ring 128 and thenallowed to passively diffuse into the volume once it is applied to thewound. Finally, gaseous or aerosolized medications or compounds may beintroduced into the gas flow entering treatment volume 122.

FIGS. 9A and 9B illustrate an alternate embodiment of the climatecontrol system discussed above wherein a fluid inlet line 140 may formpart of a barrier layer 142. Barrier layer 142 is unitary with fluidinlet line 140 and is preferably attached to an exhaust filter media 144to allow excess pressure to be released from a wound treatment volume146. In this embodiment, filter media 144 forms part of barrier layer142. The arrows “A” in FIG. 9B illustrate the movement of the fluidthrough fluid inlet line 140, treatment volume 146, and exhaust filter144.

FIG. 10 illustrates an alternate embodiment wherein an exhaust filter154 is retained in a recess 150 formed in one side of a peripheralsealing ring 152. This structure allows excess fluid to be exhaustedthrough the side of peripheral sealing ring 152, rather than through thetop, as illustrated in FIGS. 9A and 9B.

FIG. 11A is a perspective view of the embodiment illustrated in FIG. 9A,wherein a connector 160 on the end of a fluid supply line 162 engageswith an opening 164 on fluid inlet line 140. FIG. 11B illustrates a sideview of fluid supply line 162 as it engages with fluid inlet line 140.FIG. 11C illustrates the embodiment in FIGS. 11A and 11B where fluidinlet line 140 is folded over the top of peripheral sealing ring 152 toseal treatment volume 146 when supply line 162 is uncoupled.

FIG. 12 illustrates an alternate embodiment in which a fluid inlet slot170 engages with a rigid connector 172 on a fluid inlet line 174. Fluidinlet slot 170 forms an opening in one portion of a peripheral sealingring 176. The opening is in fluid communication with a treatment volume178. This configuration allows for quick disconnection of fluid inletline 174 from wound covering 180 providing the patient with additionalmobility.

FIG. 13A is a perspective view of an alternate non-contact woundcovering 190 having a fluid inlet connector 192 attached to a topsurface 194 of a peripheral sealing ring 196. Fluid inlet connector 192preferably contains an inlet filter media 198. A rigid connector 200 ona fluid inlet line 202 mates with fluid inlet connector 192. Asillustrated in FIG. 13B, a cover 204 extends from the top of fluid inletconnector 192 across the top of peripheral sealing ring 196 where itengages with an exhaust filter media 206. FIG. 14 illustrates theembodiment of FIGS. 13A and 13B utilizing a non-disposable fluid supplyline 210.

FIG. 15 illustrates an alternate embodiment which utilizes a manifoldstructure 220 as part of a fluid inlet line 222 to provide evendistribution of the fluid being introduced into a treatment volume 224.Fluid inlet line 222 preferably has a series of seals 226 along its edgewhich are interrupted by a plurality of side openings 228 from which thefluid can be transmitted into treatment volume 224. The embodimentdisclosed in FIG. 15 illustrates an exhaust filter 230 recessed into theside of peripheral sealing ring 232. However, it will be understood thata variety of exhaust filter configurations are possible with thedisclosed manifold structure 220.

FIGS. 16A and 16B illustrate an alternate wound covering 240 with a topbarrier layer 242 and a lower layer 244 having a plurality of holes 246.As is illustrated in FIG. 16B, a top cover 243 forms the barrier layer242 and it extends substantially across the area of the peripheralsealing ring 248. Lower layer 244 likewise extends across the peripheralsealing ring 248. Thus, an upper insulating layer 250 is formed betweenlower layer 244 and the top of barrier layer 242. Fluid in a fluid inletline 252 is directed into upper insulating layer 250. The pressurizedfluid in upper insulating layer 250 passes through holes 246 into atreatment volume 254. Holes 246 in lower layer 244 provide a generallyeven distribution of the fluid within wound treatment volume 254. Anoptional seal 258 may be formed in the center portion of barrier layer242 and lower layer 244 to provide these layers with additionalstructural support. An exhaust filter medium 256 is provided in a recessalong one side of peripheral sealing ring 248 to relieve pressure intreatment volume 254.

FIG. 17 illustrates an alternate embodiment of a non-contact woundcovering 260 Utilizing semi-rigid supports 262 to retain a barrier layer264 above a wound area. It will be understood by those skilled in theart that a variety of semi-rigid supports 262 may be utilized for thisapplication. For example, plastic or resilient rubber materials mayprovide sufficient support to barrier layer 264 with a minimum risk ofinjuring the patient.

FIGS. 18A and 18B illustrate an alternate exhaust filter medium 270 withan enlarged surface area to accommodate larger volumes of air flowthrough a non-contact wound covering 280. Exhaust filter 270 isincorporated into a fluid inlet line 272. Fluid inlet line 272 alsoforms a portion of a barrier layer 274, which is in turn attached to aperipheral sealing ring 276. As is best shown in FIG. 18B, fluidillustrated as the arrows “A” is introduced into a fluid inlet line 272,where it is directed into a wound treatment volume 278, past the woundarea and out through exhaust filter medium 270.

FIG. 19 illustrates a bi-directional line 290 with a center divider 292.Fluid is introduced into a fluid inlet line 294 where it proceedsthrough a fluid inlet port 296 into a treatment volume 298. The fluidthen is forced through a fluid outlet port 300 where it is driven awayfrom treatment volume 298 in a fluid outlet line 302. It will beunderstood by those skilled in the art that it would be possible toutilize separate fluid inlet and outlet lines to achieve the sameresult.

A schematic diagram of an embodiment of the present invention usingactive heating and control is depicted in FIG. 20 as an active heaterassembly 310 including a heater 312, a heater filament 314 within heater312, a controller 316, electrically coupled between heater filament 314and a power source 318 by electrical connectors 315, and using a tissuetemperature sensor 320, and an operator input interface 322 suitable foran operator to input programming parameters into controller 316. Heaterassembly 310 is useful in several different configurations, for example,as providing a heater layer for use directly in a pocket such as thatdepicted by heater 100 inserted into pocket 114 shown in FIGS. 3A and 3Bor as a heat source for warming air that is circulated over the wound asis depicted in the several embodiments of FIGS. 4 through 19.

In addition to the various suggested fluid delivered heater “geometries”depicted in FIGS. 4-19, the present invention anticipates numerouspossible heater electrical resistive filament 314 geometries. Examplesof four such geometries are shown in FIGS. 21A, B, C, and D whereinthere is depicted additional alternate heater array geometries forheating filament 314 within heater 312. In FIG. 21A, there is depicted alinear geometry for heater filament 314. This geometry is suitable fornon-uniform heating where maximum heating is desired over a linear area,such as a linear surgical wound without direct heating over adjacentperiwound areas. FIG. 21B depicts a geometry for heater filament 314consistent more as a point source. FIG. 21C depicts an ovoid geometryfor filament 314 suitable for non-uniform heating of selected periwoundarea. Alternatively, this non-uniform heating may be achievable withcircular, square, rectangular, triangular or other such geometriesdepending on the type and shape of wound encountered.

In operation, heater assembly 310 is programmable, controlling one ormore parameters, such as heater temperature, duty cycle, therapy cycleduration, number of duty cycles per therapy cycle, average heatertemperature per duty cycle, and average heater temperature per therapycycle. The programming may be preset at time of manufacture intocontroller 316 and provide a menu including treatment scenarios operatorselectable at input interface 322. Additionally, the parameterprogrammability may be entirely under the control of an operator throughinput interface 322 and suitable for inputting any number of customtreatment regimens. For example, one regimen anticipates that anoperator may input a desired tissue temperature and the target tissue isthen monitored through tissue temperature sensor 320.

Alternatively, another regimen anticipates that an operator may input atreatment paradigm using parameters based on empirical modeling oftissue temperature responses for the various types of wounds, woundsize, wound stage and wound location. Desired tissues targeted formonitoring may be the wound surface, the tissue below the wound surface,the periwound surface and tissue below the periwound surface. Empiricalmodeling may be based on parameters such as thermodynamiccharacteristics of tissue temperature conduction rates, surface area tobe treated, tissue volume to be treated, wound type, wound location,wound staging, and heater geometries and heater outputs as a few of theparadigm values. Such programmable treatment paradigms are tissuetemperature sensor independent and therefor tissue temperature sensor320 is not needed in this mode.

By way of example, and not limiting in scope of treatment versatility,FIG. 22 is a graphic representation of one such treatment regimen. InFIG. 22, several heater duty cycles have been depicted as a curve 330and the tissue temperature response as a curve 332. Time (t) isrepresented along the abscissa and temperature (T) along the ordinate. Atissue temperature target value T_(tar) 334 has been entered either byprogram or direct input from the operator and the heater started at t₀334. The tissue start temperature is at a temperature T_(a) 336 and thestaring heater temperature is at ambient temperature T_(amb) 338. Byturning on the heater at t₀ 334, the first of several duty cycles forthe heater begins in order to provide heat with which to raise thetissue temperature to T_(tar) 334. A heater operating temperature T_(h)340 is chosen by the controller based on the value, either programmed orinputted, for T_(tar) 334 and the heater controller provides theappropriate duty cycle ratio and heater cycle period so as to provide asafe and efficacious heating of at least a portion of the selected woundtreatment area. The tissue target temperature T_(tar) 334 value isreached at t₁ 342, at which time the heater is turned off.Alternatively, although not shown, upon reaching T_(tar) 334, thecontroller could have changed T_(h) 340 to a lower value and kept theheater active in order to maintain the tissue temperature at T_(tar)334.

By way of another example, and not limiting in scope of treatmentversatility, a plurality of therapy cycles are depicted in FIG. 23,wherein individual heater cycles within each therapy cycle have beenaveraged out for purposes of clarification and for purposes herein aretreated as the heater being “on”. A first therapy cycle begins at t₀ 350as depicted by the heater turning “on”, i.e., a series of heater cyclesis begun as shown by a heater temperature curve 352. A tissuetemperature target value T_(tar) 354 has been entered either by programor direct input from the operator and the tissue temperature response isshown in a curve 356. The tissue start temperature is at a temperatureT_(R) 358 and the starting heater temperature is at about ambienttemperature T_(amb) 360. The heater remains “on” until the tissuetemperature has reached T_(tar) 354 as monitored directly or aspredicted by an appropriate heating paradigm. As shown T_(tar) 354 isreached at t₁ 362 at which time the heater is turned “off”. As in theprevious example, an alternative is that the heater controller selectsan alternate heating output, chosen to maintain the tissue temperatureat about T_(tar) 354. As depicted in FIG. 23, however, the tissuetemperature is allowed to drift downwardly with the heater “off” untilthe tissue temperature reaches a temperature T_(min) 364 that is eitherprogrammed or pre-selected as a value in the selected paradigm. Uponreaching T_(min) 364, the heater is turned “on” again, as shown at t₂366, so as to provide heat to the selected treatment area to raise thetissue temperature to T_(tar) 354. This first therapy cycle ends at t₂366 when a second therapy cycle begins by turning “on” the heater again.As in the first therapy cycle, this second therapy cycle provides heatto the tissue to reach the tissue target temperature, T_(tar) 354.Alternatively this second therapy cycle may have a different T_(tar)354, or optionally may have a different cycle length calling for thecontroller to change the heater output. The present inventionanticipates the use of any number of therapy cycles having any length orduration per cycle and different set temperatures, and a plurality oftherapy cycles contributing to a therapeutic sequence.

For the above examples, T_(tar) 354 may be programmed as a paradigm ordirectly inputted into the controller. For the present invention, thistissue target temperature is in a range preferably firm a pretreatmenttemperature to about 38° C. Another aspect of therapy control accordingto the present invention is the averaging of therapy cycle andtherapeutic sequence tissue target temperatures, as depicted in FIG. 24.The example is not intended to be limiting in scope of treatmentversatility.

In FIG. 24, a therapy cycle starts at t₀ 370 and ends at t₁ 372. Thetissue target temperature average T_(ave) 374 for this therapy cycle maybe pre-selected or programmed. The tissue temperature change, asdepicted by a temperature curve 376, begins at a temperature T_(a) 376,rises as it is heated by the heater to T_(b) 378 during the “on” phaseof the heater, as depicted by a heater temperature curve 380, and thendrifts downwardly to T_(c) 382 over an additional period of time suchthat the total period of time is equivalent to the period t₀ 370 to t₁372. T_(ave) 374 represents the average of the temperatures betweenT_(a) 376 and T_(b) 378, or in the alternative the average between T_(a)376 and T_(c) 382 over the time period t₀ 370 to t₁ 372.

An alternative approach, also depicted in FIG. 24, anticipates theprogramming of a number of therapy cycles as elements of a therapeuticsequence, in this example there being two therapy cycles of varyingtimes and tissue target temperatures. The present invention provides forthe inputting of an average tissue target temperature T_(ave) 384 forthe therapeutic sequence, in this example, extending from t₀ 370 tot_(t) 386. Each of these average temperatures, whether an average over atherapy cycle or over a therapeutic sequence, is intended to have thesame temperature range from a pretreatment temperature to about 38° C. Asecondary consequence of this controller regimen is that if averagetemperatures are used, either over the therapy cycle and/or therapeuticsequence, then the resultant peak tissue temperatures may be higher thanthis range. These peak temperatures are short lived by comparison and donot represent a safety concern.

The present invention is the development of a safe, efficaciousnon-contact heater wound covering providing heat to a patient's woundfrom the heater that warms a target tissue controlled to a temperaturein a range from a pretreatment temperature to about 38° C., orcontrolled to an average temperature in a range from a pretreatmenttemperature to about 38° C. While the invention has been illustrated bymeans of specific embodiments and examples of use, it will be evident tothose skilled in the art that many variations and modifications may bemade therein without deviating from the scope and spirit of theinvention. However, it is to be understood that the scope of the presentinvention is to be limited only by the appended claims.

TABLE 1 Time Subcutaneous Temperature (in minutes) (° C. mean ± S.D.)−60 33.9 ± 1.1  0 34.7 ± 1.2  30 36.9 ± 0.6  60 37.1 ± 0.4  90 37.4 ±0.5 120 37.6 ± 0.5 180 36.0 ± 0.4 240 36.1 ± 0.2 300 35.8 ± 0.6

TABLE 2 Time Skin Temperature Inside Covering (in minutes) (° C. mean ±S.D.) −60 33.2 ± 1.1  0 33.9 ± 1.1  30 36.7 ± 0.5  60 37.0 ± 0.4  9037.1 ± 0.4 120 37.2 ± 0.4 180 35.2 ± 0.5 240 35.2 ± 0.4 300 35.1 ± 0.5

TABLE 3 Time Laser Doppler Flow (in minutes) (ml/100 g/min ± S.D.) −6064 ± 42  0 110 ± 100  30 199 ± 191  60 178 ± 131  90 222 ± 143 120 271 ±235 180 158 ± 146 240 146 ± 125 300 173 ± 158

TABLE 4 Time Subcutaneous Oxygen Tension (P_(sq)O₂) (in minutes) (mm Hgmean ± S.D.) −60  54 ± 10  0 110 ± 60  30 109 ± 58  60 122 ± 59  90 136± 57 120 159 ± 55 180 153 ± 60 240 156 ± 61 300 148 ± 52

TABLE 5 Time Subcutaneous Temperature (in minutes) (° C.) −60 33.8 ± 1.5 0 35.2 ± 1.5  30 37.1 ± 1.1  60 37.3 ± 0.8  90 37.4 ± 0.7 120 37.3 ±0.8 180 35.8 ± 1.2 240 35.8 ± 1.0 300 36.1 ± 0.9

TABLE 6 Time Skin Temperature Inside Covering (in minutes) (° C.) −6032.9 ± 1.5  0 34.5 ± 1.0  30 37.1 ± 0.6  60 37.5 ± 0.5  90 37.6 ± 0.5120 37.6 ± 0.5 180 34.9 ± 0.8 240 35.0 ± 0.7 300 35.2 ± 0.6

TABLE 7 Time Laser Doppler Flow (in minutes) (ml/100 g/min) −60 44 ± 22 0  95 ± 132  30 142 ± 155  60 191 ± 150  90 207 ± 209 120 161 ± 91  18073 ± 29 240 70 ± 30 300 71.5 ± 25  

TABLE 8 Time Subcutaneous Oxygen Tension (P_(sq)O₂) (in minutes) (mm Hg)−60  58 ± 11  0 123 ± 73  30 128 ± 67  60 145 ± 69  90 157 ± 73 120 153± 55 180 148 ± 73 240 142 ± 73 300 143 ± 76

1. A covering for application to a tissue treatment area of a patient'sbody, said covering comprising: a heater for providing heat to at leasta portion of the tissue treatment area; flexible attachment means forattaching the heater in a non-contact position proximate the tissuetreatment area; and a controller connected to the heater for causing theheater to raise the temperature of tissue in the tissue treatment areato a temperature in a range from a pretreatment temperature to 38° C. 2.An apparatus for treating tissue on a patient's body, the apparatuscomprising: an attachment device having a first and a second surface,and an opening; a layer on the first surface, over the opening; anattachment portion at the second surface; and, a heater supported by thelayer, over the opening; a controller to cause the heater to raise thetemperature of tissue under the opening to a temperature in a range froma pretreatment temperature to 38° C.
 3. The apparatus of claim 2,wherein the opening extends from the first surface to the secondsurface.
 4. The apparatus of claim 2, in which the heater is an activeheater.
 5. The apparatus of claim 2, in which the heater is selectedfrom the group containing warm water pads, chemical heating pads, andphase-change salt pads.
 6. The apparatus of claim 2, the controllerincluding a means for causing the heater to raise the temperature of thetissue from the pretreatment temperature to 38° C.
 7. The apparatus ofclaim 6, in which the heater is an active heater.
 8. The apparatus ofclaim 7, which the heater is an electrical heater.
 9. The apparatus ofclaim 2, further including means on the layer for receiving the heater.10. The apparatus of claim 2, in which the attachment device is a ring.11. The apparatus of claim 10, in which the ring is a sealing ring. 12.The apparatus of claim 11, in which the sealing ring is made of apolymeric foam material.
 13. The apparatus of claim 2, the controllerincluding means for causing the heater to operate at an averagetemperature over a therapeutic sequence.
 14. The apparatus of claim 2,the therapeutic sequence including a plurality of therapy cycles. 15.The apparatus of claim 2, the controller including means for cycling theoperation of the heater on and off.
 16. The apparatus of claim 15,wherein the controller includes programmable means for cycling theoperation of the heater over a duty cycle.
 17. The apparatus of claim15, wherein the controller includes programmable means for cycling theoperation of the heater over a therapy cycle.
 18. The apparatus of claim17, wherein the therapy cycle includes a plurality of duty cycles. 19.The apparatus of claim 15, wherein the controller includes programmablemeans for controlling the operation of the heater over a therapeuticsequence, the therapeutic sequence including one or more therapy cycles,each therapy cycle including one or more duty cycles.
 20. The apparatusof claim 2, wherein the controller includes selectable averagetemperature values, each indicating an average temperature of theheater.
 21. The apparatus of claim 2, the controller including means forcausing the heater to operate at an average temperature over a dutycycle.
 22. The apparatus of claim 2, the controller including means forcausing the heater to operate at an average temperature over a therapycycle.
 23. The apparatus of claim 2, the controller including means forcausing the heater to operate at an average temperature over atherapeutic sequence.
 24. The apparatus of claim 23, the therapeuticsequence including a plurality of therapy cycles.
 25. The apparatus ofclaim 24, each therapy cycle including a plurality of duty cycles.